Quote:
Originally Posted by GMB
Quote:
Originally Posted by kalee20
Suppose you wind the primary, and then put on a single turn of foil which you earth. And then start winding the 240V secondary....
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That's why you don't do it like that. Safety transformers have separate bobbins so we just need to add enough screening so that the secondary cannot "see" the mains and you can get a good result. Actually it may be enough to earth the laminations if the bobbins are far enough apart.
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Good point, and yes it would give better isolation and lower capacitance of the floating secondary to everything else.
Although, most of the isolating transformers that I've seen, have been as I've described. The twin-section bobbin type is the exception rather than the rule. It also has slightly less-good regulation, due to higher leakage inductance.